Using an integrated luminosity of 475 fb1 collected near 10.58 GeV by the BaBar detector, we have measured the natural line width of the D+ meson to be = (83:31:31:4) keV and the D+ D0 mass dierence pole position to be m0 = (145 425:80:51:8) keV. The width measurement is about 12 times more precise than the best previous measurement, and the mass dierence a factor of 6. The width measure- ment reinforces the observed non-universality of the strong coupling strength gDD which is expected to be a constant in a chiral quark model. We have also measured the D0 mass to be m(D0) = (1864:841 0:048 0:062) MeV. This result is more than twice as precise as the best published measurement and helps constrain interpretations of the X(3872).